How smart was Paraptenodytes?

It’s hard to quantify intelligence in a bird. They won’t sit still for an IQ test and may not have learned geometry in their early years anyway. While some birds such as parrots can actually develop a vocabulary of human words, penguins stick mostly to rather harsh braying sounds. Although we can’t give them a grade, we do know that penguins have many complex behaviors, including bonding rituals shared with mates, coordinating “rafts” of multiple birds to come ashore smoothly, and even a penchant for stealing from other penguins. These observations suggest penguins are smart animals overall.

What about fossil penguins? Paleontologists have one neat tool to estimate intelligence – Encephalization Quotient (EQ). EQ is a measure of the brain size of an animal relative to its body size. EQ controls for allometry – that is, it corrects for the fact that larger animals have smaller brains relative to absolute size. An elephant’s brain accounts for only about 0.2% of its total mass, while a cat’s accounts for a whole 1%. However, when you control for size scaling, both have an EQ of around 1, which is the baseline for mammals. Biologists calculate whether an animal is above average or below average by plotting out brain mass versus body mass for a large group of species and then checking whether a particular species falls above the line or below the line. EQ levels roughly correlate to intelligence, with the highest levels seen in chimpanzees (2.5) dolphins (4) humans (7.5).

Because only the size of the brain and an estimate of mass is needed, it is possible to calculate for extinct species by either physical means or virtual means. Filling the braincase with millet grains to estimate volume was one early technique. Today paleontologists often use CT data for determining brain volume.

Plot of bird brain size versus body mass. Points above the solid line have larger than expected brains and points below the solid line have smaller than expected brains. Paraptenodytes is represented by the star.

We plotted the brain size and body mass of a variety of bird species in our study, and found that Paraptenodytes falls a little bit above the line, suggesting it was a quick-witted penguin. There is something else to consider about the plots though. Penguins are much denser than other birds because of their solid bones and the thick fat layers they build up for insulation. So, a penguin that is roughly the same size as a bird like a seagull will weight more. We used mass as the measurement to make the plots, but if we used another measurement like body length or standing height, the penguins would move up higher above the curve, Does that mean penguins really have a higher encephalization quotient? It’s hard to say. Perhaps they just require more cerebral volume to control their heavier bodies. Alternatively, penguins may need enlarged brains to survive in the very complex world they inhabit. Spending part of their time hunting at sea and part of their time moving about on land to build nests, raise chicks and socialize with other birds in their colonies involves a lot of different, complex behaviors. It may take a high-power brain just to keep all up with all these activities.

March of the Fossil Penguins

written by Dr. Daniel Ksepka

This blog details fossil discoveries and research on the fascinating Sphenisciformes. The aim is to introduce the cast of fossil species (50 and counting), explore the evolutionary history of penguin bones, feathers and ecology, and explain how scientists learn about life in the past.